Deion Jefferson, 10, and Samuel Jefferson, 7, take turns climbing and jumping off a stack of old tires at the Berkeley Adventure Playground in California. The playground is a half-acre park with a junkyard feel where kids are encouraged to "play wild."

An overview of the Berkeley Adventure Playground, where children and their parents can paint, hammer, saw and run free.

David Gilkey/NPR

This week, NPR Ed is focusing on questions about why people play and how play relates to learning.

When it comes to brain development, time in the classroom may be less important than time on the playground.

"The experience of play changes the connections of the neurons at the front end of your brain," says Sergio Pellis, a researcher at the University of Lethbridge in Alberta, Canada. "And without play experience, those neurons aren't changed," he says.

It is those changes in the prefrontal cortex during childhood that help wire up the brain's executive control center, which has a critical role in regulating emotions, making plans and solving problems, Pellis says. So play, he adds, is what prepares a young brain for life, love and even schoolwork.

But to produce this sort of brain development, children need to engage in plenty of so-called free play, Pellis says. No coaches, no umpires, no rule books.

"Whether it's rough-and-tumble play or two kids deciding to build a sand castle together, the kids themselves have to negotiate, well, what are we going to do in this game? What are the rules we are going to follow?" Pellis says. The brain builds new circuits in the prefrontal cortex to help it navigate these complex social interactions, he says.

Learning From Animals

Much of what scientists know about this process comes from research on animal species that engage in social play. This includes cats, dogs and most other mammals. But Pellis says he has also seen play in some birds, including young magpies that "grab one another and start wrestling on the ground like they were puppies or dogs."

For a long time, researchers thought this sort of rough-and-tumble play might be a way for young animals to develop skills like hunting or fighting. But studies in the past decade or so suggest that's not the case. Adult cats, for example, have no trouble killing a mouse even if they are deprived of play as kittens.

So researchers like Jaak Panksepp at Washington State University have come to believe play has a very different purpose: "The function of play is to build pro-social brains, social brains that know how to interact with others in positive ways," Panksepp says.

Panksepp has studied this process in rats, which love to play and even produce a distinctive sound he has labeled "rat laughter." When the rats are young, play appears to initiate lasting changes in areas of the brain used for thinking and processing social interactions, Panskepp says.

The changes involve switching certain genes on and off. "We found that play activates the whole neocortex," he says. "And we found that of the 1,200 genes that we measured, about one-third of them were significantly changed simply by having a half-hour of play."

Of course, this doesn't prove that play affects human brains the same way. But there are good reasons to believe it does, Pellis says.

For one thing, he says, play behavior is remarkably similar across species. Rats, monkeys and children all abide by similar rules that require participants to take turns, play fair and not inflict pain. Play also helps both people and animals become more adept socially, Pellis says.

And in people, he says, an added bonus is that the skills associated with play ultimately lead to better grades. In one study, researchers found that the best predictor of academic performance in eighth grade was a child's social skills in third grade.

Another hint that play matters, Pellis says, is that "countries where they actually have more recess tend to have higher academic performance than countries where recess is less."

Copyright 2014 NPR. To see more, visit http://www.npr.org/.

Transcript

STEVE INSKEEP, HOST:

Important as they are, some of today's big news headlines may have less effect on the future than what's happening today on countless playgrounds. That's where children are passing time and also developing their minds. NPR's Jon Hamilton has the latest report in our series, Playing To Learn.

JON HAMILTON, BYLINE: To some people this may sound like chaos. But to Sergio Pellis, a researcher at the University of Lethbridge in Canada, it's the sweet music of new brain circuits taking shape.

SERGIO PELLIS: The experience apply changes the connections of the neurons at the front end of your brain, which are a major part of the executive control system of your brain. And without play experience those neurons aren't changed.

HAMILTON: The brain's executive control system helps regulate emotions, make plans and solve problems. And Pellis says, for the system to develop properly children need plenty of so-called, free play, no coaches, no umpires, no rulebooks.

PELLIS: In freely chosen play, whether that's rough-and-tumble play or two kids deciding to build a sand castle together, the kids themselves have to negotiate, well what are we going to do in this game? What are the rules we're going to follow? And what am I going to do if my friend's now cheating on the rules that we agreed to?

HAMILTON: Pellis says the brain builds new circuits to help it navigate these complex social interactions. Much of what scientists know about this process comes from research on animals, cats, dogs and most other mammals play. So, do some birds. Pellis says he realized this while studying magpies.

PELLIS: Two young magpies grab one another and start wrestling on the ground like they were puppies or dogs.

HAMILTON: For a long time researchers thought this sort of play might be a way for young animals to develop skills like hunting or fighting. But studies suggest that's not the case. Adult cats for example have no trouble killing a mouse, even if they are deprived of play as kittens. So, researchers like Jaak Panksepp, at Washington State University, have come to believe that play has a very different purpose.

JAAK PANKSEPP: The function of play is to build pro-social brains - social brains that know how to interact with others in positive ways.

HAMILTON: Panksepp has studied this process in rats. He says they love to play and make a lot of noise while they're at it.

(SOUNDBITE OF RAT NOISES)

PANKSEPP: We were able to find this marker of playfulness, which we call, rat laughter.

HAMILTON: It's normally pitched too high for the human ear. So, this sample was converted to a lower frequency. In rats, play appears to make lasting changes in areas of the brain used for thinking. Panksepp says it does this by switching certain genes on and off.

PANKSEPP: We found that play activates the whole neocortex. And we found that of the 1,200 genes that we measured about one third of them were significantly changed simply by having half an hour of play.

HAMILTON: The question is whether play affects humans' brains the same way. And Sergio Pellis, the researcher from Canada, says there are good reasons to believe it does. For one thing he says, play behavior is remarkably similar across species.

PELLIS: The rough-and-tumble play that you see in rats and monkeys and people has a certain rule structure.

HAMILTON: You have to take turns, play fair and try not to inflict pain. Pellis says play also makes both people and animals more adept socially. And more attractive to the opposite sex. In people he says, an added bonus is that the skills associated with play also lead to better grades. He says one study measured social skills and academic performance in third grade, then again in eighth grade.

PELLIS: And we can ask which of the two data sets, social skills or academic performance is a better predictor of their academic performance at eighth grade? And it turns out that the better predictor is social skills.

HAMILTON: Which depends on playtime not class time. And Pellis says, there's one more bit of evidence that play can boost a child's grades.

PELLIS: Countries where they actually have more recess, academic performance tends to be higher than countries where recess is less.